Brain Builder

 Brain Builder:

The water level in a reservoir is low, but it doubles everyday. It takes 60 days to fill the reservoir. How long does it take for the reservoir to become half full?

 

Answer:

59 days. The water level doubles everyday, so on any given day it was half the volume on the previuos day. If the reservoir is full on day 60, that means it was half full on day 59!